It’s not every company that makes waves over new job postings, but Apple is not every company. Apple has two positions open for iOS engineers to work on the next generation of Siri, the voice-powered personal assistant for the iPhone 4S.

The new posts mention that the engineers will be working on a Siri API, which would allow applications to use the voice recognition functionality to carry out a variety of tasks.

The contents of the job announcements are important because they indicate the future direction of voice-controlled Apple products on iOS. Apple’s job posts are loaded with enticement for talented and ambitious coders, and they read like marketing material. The company asks:

Want to make the next big thing even bigger?
Want to do the impossible?
Want to be constantly challenged into accomplishing things you know are beyond your reach?

Clearly, slackers need not apply. Since the iPhone 4S launch in October, Siri has captured the public imagination and driven tremendous phone sales. Apple sold 4 million iPhone 4S units in its first weekend alone.

Siri user interface manager Dan Keen used his personal Twitter account to broadcast the job postings, which may have set off the frenzy. Keen was previously a senior software engineer for the iPhone, and has been with Apple since 2006, according to his LinkedIn profile. Keen joined the Siri UI team just three months ago.

The junior engineer position will work to improve the user experience of the Siri results page, and how it appears on the phone. “Consider it an entire miniature OS within the OS, and you get a good idea of the scope!,” Apple writes. Importantly, they want someone who can squeeze the maximum performance from the phone without draining battery life, or sacrificing on the overall experience.

You will primarily be responsible for implementing the conversation view and its many different actions. This includes defining a system that enables a dialog to appear intuitive, a task that involves many subtle UI behaviors in a dynamic, complex system. You will have several clients of your code, so the ability to formulate and support a clear API is needed.

It’s unclear whether the API would be used for third-party developers, or strictly for in-house purposes. The prospects are still tantalizing. If Apple develops its own television integrated with Siri, it should be more than enough to keep developer’s hands full for now.

And while Apple is busy preparing for the future of Siri, it would be well-advised to shore up the present. Repeated server outages and other technical issues have led some to call Siri “Apple’s broken promise.”